The present invention generally concerns an input and control device, and more specifically, a joystick that provides control signals for controlling machinery, computer games, and the like.
Joysticks are used to provide input control signals for controlling machinery and computer application programs, such as computer games. A typical joystick includes a handle that is pivotally rotatable about a base, producing an output signal corresponding to the angular displacement of the handle about orthogonal xe2x80x9cXxe2x80x9d and xe2x80x9cYxe2x80x9d axes. It should be noted that movement of the joystick handle is sometimes referred to in terms of its motion in the direction of planar X and Y axes, rather than rotation about these axes. The output signal from a joystick is typically input to a receiving device, such as a computer, which processes the signal so that it may be used to control hardware or to provide a command input to a computer software program. For example, in a computer running an aircraft simulator program, a forward or reverse movement of the joystick""s handle about the X axis causes an output signal to be generated that is used to control the elevators of the aircraft and thus affects the pitch of the aircraft, while lateral movement of the joystick about the Y axis produces a corresponding output signal that is used to control the ailerons, and thus affects roll or rotation of the aircraft about its longitudinal axis.
Joysticks are generally designed to function as either on/off devices or proportional devices. Lower-cost on/off devices only operate positional switches to provide an indication of whether a minimum displacement of the control handle about one or both axes of the joystick has occurred, whereas proportional devices provide output signals having a magnitude corresponding to a proportional displacement of the joystick control handle away from a known point, generally its xe2x80x9ccenterxe2x80x9d point. Higher-performance software applications, such as flight simulators, require the use of joysticks that provide proportional output signals.
In addition to providing X and Y axis input signals to a computer or other device, some joysticks additionally provide input signals corresponding to a third input axis, which is commonly referred to as the xe2x80x9cZxe2x80x9d axis. The Z axis generally corresponds to the centerline of the joystick""s control handle, and the Z axis output signal typically is indicative of a rotational angular displacement of the joystick handle about its centerline.
Many joysticks enable movement of the control handle about the X and Y axes through the use of a ball and socket configuration for mounting the control handle to a base. In this configuration, a ball is connected toward the lower end of the control handle shaft such that when a force is applied to the joystick""s control handle, the ball is caused to rotate in the socket. In general, these devices provide a circular opening through which the control handle shaft extends. As a result, a simultaneous maximal displacement about both the X and Y axes is not possible, since the circular opening limits the simultaneous maximal displacement about both axes to be less than the maximal displacement about a single axis. Furthermore, in this type of configuration, is also not possible to rotate the joystick control handle through a full range of motion along one axis while maintaining the other axis at a maximal displacement. Accordingly, it would be beneficial to provide a joystick that does not have these limitations.
In general, most joysticks employ various electromechanical position sensors to measure rotation of the joystick control handle relative to its central position. In joysticks that employ the ball and socket configuration, the rotation of the control handle about (or linear displacement in the direction of) the X and Y axes are generally measured using electromechanical position sensors, such as rotary or linear potentiometers, optical encoders, linear displacement voltage transducers (LDVTs), etc., which are coupled to the shaft and/or ball in various ways.
Optical position sensors have also been employed for monitoring the position of a joystick control handle. For example, in U.S. Pat. No. 5,694,153, a joystick is disclosed that measures the position of X and Y axes, and rotation about the Z axis through use of a two-dimensional light-detecting element. A pair of light emitting diodes (LEDs) are mounted at an end of the joystick""s control handle shaft and oriented toward the interior of the joystick""s housing. The LEDs are strobed to alternately project light downwardly into the housing. A light detecting element, such as a two-dimensional position sensing device (PSD), two one-dimensional PSDs, or a four quadrant photodiode, is positioned opposite the LEDS, and mounted in the housing to receive the light from the LEDs, producing analog signals corresponding to the amount of light detected. The analog signals are converted to a digital format and input to a processor that employs a triangulation algorithm to determine the position of the joystick control handle relative to each of the X, Y, and Z axes. While this scheme produces an adequate measurement of displacement about these axes, the optical components and signal processing circuitry are relatively expensive. As a result, the cost to manufacture this type of joystick is greater than desired.
Durability is also an important feature for a joystick. It is very common for a user to apply significant forces to a joystick handle when playing games. The excessive force is due to a typical user""s excitement during the game, when the user has a natural tendency to push the joystick handle harder in an attempt to achieve a faster or stronger response. The forces exerted by a user can be sufficient to damage the joystick control handle or its mount to the base. Therefore, it is desirable to provide a joystick with sufficient durability to minimize the risk of such damage.
In accord with the present invention, a joystick is provided that addresses many of the foregoing limitations in the prior art. Input signals are produced by the joystick for controlling computer software programs and hardware devices in response to a pivotal displacement of a joystick control handle about a center point relative to two orthogonal axes that pass through the center point referred to as the xe2x80x9cXxe2x80x9d and xe2x80x9cYxe2x80x9d axes. Preferably, the device further provides a third input axis (the xe2x80x9cZxe2x80x9d axis), about which rotation of a joystick control handle produces an input signal. The rotation about each axis is measured by separate position sensors that each produce a proportional output signal indicative of angular displacement of the control handle about a different one of these three axes. Springs that resists displacement of the joystick about each of the X, Y, and Z axes are also provided such that the joystick is automatically returned to a center position for each axis when input force on the joystick handle is removed.
The joystick includes a shaft extending from the control handle that is coupled to an end cap defining a spherical surface. In addition, a hemispherical-shaped member comprising a spherical exterior surface is coupled to the shaft adjacent towards a middle portion of the shaft. Preferably, the hemispherical-shaped member comprises a substantially hemispherical shell having four arcuate reliefs defined in respective quadrants of the shell. The shaft extends into an opening formed in a top portion of the housing. A bearing surface adapted to slidingly engage the spherical exterior surface of the hemispherical-shaped member as the joystick is pivoted is provided in the housing. A bottom portion of the housing, which is coupled to the top portion, includes a receiver adapted to slidingly engage the spherical surface of the end cap. Preferably, the spherical exterior surface of the hemispherical-shaped member and the spherical surface of the end cap are configured such that each of these surfaces share a common center point. Accordingly, movement by a user of the joystick control handle causes the control handle to be pivotally displaced about this common center point.
Preferably, the direction and magnitude of such a pivotal displacement can be determined by measuring a corresponding rotation about two orthogonal axes (the X and Y axes) that pass through the center point. Thus, a first position sensor and a second position sensor are operatively coupled to the control handle shaft so as to produce a signal that is proportional to an angular rotation of the joystick about the X and Y axes. The first and second position sensors preferably comprise potentiometers, so that a direction and a magnitude of the pivotal displacement of the joystick control handle can be readily determined as a function of output voltage signals produced by the potentiometers.
The potentiometers are operatively coupled to the shaft through gimbals. An upper gimbal is pivotally mounted to the housing and comprises a yoke connected at opposing ends to support shafts having a common centerline coincident with the X axis and a slot defined therein, parallel to the first axis through which the control handle shaft extends. The slot is also adapted to slidingly engage the control handle shaft such that the control handle shaft can freely rotate about the Y axis without causing the gimbal to rotate about the X axis. Preferably, the yoke includes a substantially hemispherical shell that is nested below the hemispherical member connected to the shaft of the joystick control handle. A substantially similar lower gimbal, having a substantially hemispherical yoke and an axis of rotation corresponding to the Y axis, is likewise pivotally mounted to the housing. The configuration of the upper and lower gimbals is such that the yoke of the lower gimbal is nested just below the upper gimbal and the gimbals rotate about orthogonal axes that share a common crossing point, preferably coincident with the center point discussed above. The yoke of the lower gimbal also has a slot defined therein, extending parallel to the Y axis through which the shaft of the joystick control handle extends and is adapted to slidingly engage this shaft, enabling the shaft to be rotated freely about the X axis without causing rotation of the lower gimbal about the Y axis.
Each of the upper and lower gimbals is operatively coupled to a spring that develops a bias force applied against the joystick control handle when the control handle is pivotally displaced away from the center position about the X and Y axes. Preferably, each of the springs comprises a torsion spring including a looped portion having a pair of tangs extending therefrom. The torsion spring is disposed in a holder and coupled to a support shaft on one of the gimbals. The holder and housing are configured such that when the joystick is in a centered position with respect to one of the X and Y axes, the tangs of the torsion spring corresponding to that one axis engage the housing and the holder in a manner that exerts no torque on the holder (and thus, no torque on the respective gimbal). However, rotation of the joystick in either direction about an axis of the gimbal causes a distance between the tangs to change such that one of the tangs exerts a force against the housing while the other tang exerts a force against the holder, thereby generating a torque opposite the direction of the rotation of the control handle about the gimbal axis. As a result, a bias force is produced that is exerted upon the control handle opposite the direction of its displacement.
The joystick is configured so as to enable a full range of motion to be traversed about one of the X and Y axes, while simultaneously enabling a user to maintain a maximal displacement about the other axis.
Rotation of the control handle about a third (xe2x80x9cZxe2x80x9d) axis, i.e., a longitudinal axis of the shaft by a user, produces a third input signal. Preferably, the shaft of the joystick control handle is prevented from rotating about this longitudinal axis by a flat formed on the shaft that engages the slots in at least one of the gimbals. A position sensor, preferably a potentiometer, produces a signal indicative of the angular position of the control handle as the control handle is rotated about its longitudinal axis. Preferably, the third axis also includes a spring configured in a manner substantially similar to the springs used for the X and Y axes, to provide a bias force to return the control handle to a center position about the Z axis when the joystick handle is rotated away from its center position. A force is exerted on the control handle by the spring to oppose rotation of the control handle by a user.
Electronic circuitry in the joystick include a memory in which is stored calibration data used for correcting offsets and scaling errors in the output signals produced by the joystick without requiring a user to perform a calibration process. Additionally, the electronic circuitry recalibrates the control signals in the event of component wear and enables positive identification of each different joystick if a plurality of identical joysticks are connected to the same Universal Serial Bus (USB) port on a computer.